Ronald A. Downes

A Catalog and Atlas of Cataclysmic Variables: The Living Edition

ABSTRACT The Catalog and Atlas of Cataclysmic Variables (Edition 1: Downes & Shara; Edition 2: Downes, Webbink, & Shara) has been a valuable source of information for the cataclysmic variable community. However, the goal of having a central location for all objects is slowly being lost as each new edition is generated. There can also be a long time delay between new information becoming available on an object and its publication in the catalog. To eliminate these concerns, as well as to make the catalog more accessible, we have created a Web site which will contain a “living” edition of the catalog. We have also added orbital period information, as well as finding charts for novae, to the catalog.

Optical Imaging of Nova Shells and the Maximum Magnitude-Rate of Decline Relationship*

An optical imaging study of 30 recent novae has been undertaken using both ground-based and space-based observations. Resolved shells have been detected around nine objects in the ground-based data, while another four objects have shells detected by Hubble Space Telescope observations; for RW UMi, we fail to detect a shell that was observed 5 years earlier. Images in H?, and when appropriate [O III] ?5007, are shown, and finding charts for novae without shells are given if no published chart is available. Expansion parallaxes for all systems with shells are derived, and absolute magnitudes for a total of 28 objects are presented, along with a discussion of the maximum magnitude?rate of decline relation. We find that separate linear fits for fast and slow novae may be a better representation of the data than a single, global fit. At minimum, most novae have similar magnitudes as those of dwarf novae at maximum and nova-like stars.

Cataclysmic Variables from Sloan Digital Sky Survey. V. The Fifth Year (2004)

This paper identifies the cataclysmic variables that appear in spectra obtained in 2004 as part of the Sloan Digital Sky Survey. Spectra of 41 objects, including seven systems that were previously known (CC Cnc, DW Cnc, PQ Gem,AR UMa,AN UMa,RXJ1131.3+4322,andUMa6)and34new cataclysmicvariablesarepresented.The positions and ugriz photometry of all 41 systems are given, as well as additional follow-up spectroscopic, photometric, and/or polarimetric observations of eight of the new systems. The new objects include three eclipsing systems, six with prominent He ii emission, and six systems that show the underlying white dwarf.

A CATALOG AND ATLAS OF CATACLYSMIC VARIABLES-SECOND EDITION

We present a catalog of all 1020 known cataclysmic variables (CVs). This paper is a major update of the first edition of the catalog (Downes and Shara 1993, PASP, 105, 127), which contained coordinates (measured in the reference frame of the Hubble Space Telescope Guide Star Survey for the non-novae, and obtained from the literature for the novae), the variability type, the magnitude range, and references to both finding charts and spectroscopy. Also included in the catalog were finding charts for all dwarf novae, novalike variables, and objects classified only as cataclysmic variables known as of 1993; a similar catalog and atlas for novae has been published by Duerbeck (1978a). This updated edition includes 195 new objects (172 CVs and 23 non-CVs), revised identifications for 57 objects, and revised information (classification and spectral references) when available. We also now include plate identification information for the coordinate measurements, a reference to the classification, proper motion information where appropriate, and a table showing the CVs observed by space-based observatories. This second edition is inclusive of the first edition, although only new or updated charts are presented.

A catalog and Atlas of cataclysmic variables

The General Catalog of Variable Stars contains information necessary for obtaining observaitons of variable stars, and in particular, cataclysmic variables. However, the coordinates presented are not accurate enough for observatories such as the Hubble Space Telescope, and the references to finding charts are often to journals not easily accessible to some astronomers. We have therefore created a catalog of all cataclysmic variables (known to us as of 1992 February) which contains coordinates (measured in the reference frame of the Hubble Space Telescope Guide Star Survey for the non-novae, and obtained from the literature for the novae), the variability type, the magnitude range, and references to both finding charts and spectroscopy. The atlas contains finding charts for the dwarf novae, novalike variables, and objects classified only as cataclysmic variables, for which we could obtain valid identifications; a similar catalog and atlas for novae has been published by Duerbeck (1987a).

Spectroscopic observations of H-alpha emission stars from the Stephenson and Stephenson-Sanduleak lists

Spectroscopic observations were obtained for 111 objects from the lists of H-alpha emission stars of Stephenson (1986) and Stephenson and Sanduleak (1977). A total of 26 T Tauri stars, six symbiotic stars, three cataclysmic variables, 17 Be stars, five Me stars, two forbidden BQ stars, two emission-line galaxies, one planetary nebula, and one carbon star with Balmer emission was discovered. Descriptions are given for the spectra of the more unsual objects. A total of 47 objects failed to show emission.

Faint High-Latitude Carbon Stars Discovered by the Sloan Digital Sky Survey: An Initial Catalog

A search of more than 3000 deg2 of high-latitude sky by the Sloan Digital Sky Survey has yielded 251 faint high-latitude carbon stars (FHLCs), the large majority previously uncataloged. We present homogeneous spectroscopy, photometry, and astrometry for the sample. The objects lie in the 15.6 < r < 20.8 range and exhibit a wide variety of apparent photospheric temperatures, ranging from spectral types near M to as early as F. Proper-motion measurements for 222 of the objects show that at least 50%, and quite probably more than 60%, of these objects are actually low-luminosity dwarf carbon (dC) stars, in agreement with a variety of recent, more limited investigations that show that such objects are the numerically dominant type of star with C2 in the spectrum. This SDSS homogeneous sample of ~110 dC stars now constitutes 90% of all known carbon dwarfs and will grow by another factor of 2–3 by the completion of the survey. As the spectra of the dC and the faint halo giant C stars are very similar (at least at spectral resolution of 103), despite a difference of 10 mag in luminosity, it is imperative that simple luminosity discriminants other than proper motion be developed. We use our enlarged sample of FHLCs to examine a variety of possible luminosity criteria, including many previously suggested, and find that, with certain important caveats, JHK photometry may segregate dwarfs and giants.

Time-Resolved Ultraviolet Observations of the Globular Cluster X-Ray Source in NGC 6624: The Shortest Known Period Binary System

Using the Faint Object Spectrograph (FOS) aboard the Hubble Space Telescope (HST), we have obtained the first time-resolved spectra of the King et al. (1993) ultraviolet-bright counterpart to the 11 minute binary X-ray source in the core of the globular cluster NGC 6624. This object cannot be readily observed in the visible, even from HST, because of a much brighter star superposed less than 01 away. Our FOS data show a highly statistically significant ultraviolet flux modulation with a period of 11.46 ± 0.04 minutes, very similar to the 685 s period of the known X-ray modulation, definitively confirming the association between the King et al. (1993) ultraviolet counterpart and the intense X-ray source. The ultraviolet amplitude is very large compared with the observed X-ray oscillations: X-ray variations are generally reported as 2%-3% peak to peak, whereas our data show an amplitude of about 16% in the 126-251 nm range. A model for the system by Arons & King (1993) predicts periodic ultraviolet fluctuations in this shortest known period binary system, because of the cyclically changing aspect of the X-ray heated face of the secondary star (perhaps a very low mass helium degenerate). However, prior to our observations, this predicted modulation has not been detected. Employing the Arons & King (1993) formalism, which invokes a number of different physical assumptions, we infer a system orbital inclination 35° i 50°. Among the three best-studied ultraviolet/optical counterparts to the intense globular cluster X-ray sources, two are now thought to consist of exotic double-degenerate ultrashort-period binary systems.

H-alpha images of the Cygnus Loop - A new look at shock-wave dynamics in an old supernova remnant

Attention is given to deep H-alpha images of portions of the east, west, and southwest limbs of the Cygnus Loop which illustrate several aspects of shock dynamics in a multiphase interstellar medium. An H-alpha image of the isolated eastern shocked cloud reveals cloud deformation and gas stripping along the clouds edges, shock front diffraction and reflection around the rear of the cloud, and interior remnant emission due to upstream shock reflection. A faint Balmer-dominated filament is identified 30 arcmin further west of the remnants bright line of western radiative filaments. This detection indicates a far more westerly intercloud shock front position than previously realized, and resolves the nature of the weak X-ray, optical, and nonthermal radio emission observed west of NGC 6960. Strongly curved Balmer-dominated filaments along the remnants west and southwest edge may indicate shock diffraction caused by shock wave passage in between clouds.

M5 V101 - A close binary system in a globular cluster

Spectrophotometric and photographic observations of the large amplitude variable V101 in the globular cluster M5 show it to have the characteristics of a dwarf nova. In particular, a spectrum obtained with the Hale 5 m reflector of the object in quiescence (V approximately equal to 20) shows strong, broad Balmer and He I emission. It is suggested that M5 V101 is the strongest case for the existence of close binary systems in globular clusters.